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/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package spark.resource;

import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URL;

/**
 * Interface for a resource descriptor that abstracts from the actual
 * type of underlying resource, such as a file or class path resource.
 * An InputStream can be opened for every resource if it exists in
 * physical form, but a URL or File handle can just be returned for
 * certain resources. The actual behavior is implementation-specific.
 *
 * @author Juergen Hoeller
 * @see #getInputStream()
 * @see #getURL()
 * @see #getURI()
 * @see #getFile()
 * @see ClassPathResource
 * @see InputStreamResource
 * Code copied from Spring source. Modifications made (mostly removal of methods) by Per Wendel.
 */
public interface Resource extends InputStreamResource {

    /**
     * Return whether this resource actually exists in physical form.
     * 
This method performs a definitive existence check, whereas the
     * existence of a {@code Resource} handle only guarantees a
     * valid descriptor handle.
     *
     * @return if exists
     */
    boolean exists();

    /**
     * Return whether the contents of this resource can be read,
     * e.g. via {@link #getInputStream()} or {@link #getFile()}.
     * 
Will be {@code true} for typical resource descriptors;
     * note that actual content reading may still fail when attempted.
     * However, a value of {@code false} is a definitive indication
     * that the resource content cannot be read.
     *
     * @return if readable
     * @see #getInputStream()
     */
    boolean isReadable();

    /**
     * Return whether this resource represents a handle with an open
     * stream. If true, the InputStream cannot be read multiple times,
     * and must be read and closed to avoid resource leaks.
     * 
Will be {@code false} for typical resource descriptors.
     *
     * @return if open
     */
    boolean isOpen();

    /**
     * @return a URL handle for this resource.
     * @throws IOException if the resource cannot be resolved as URL,
     *                     i.e. if the resource is not available as descriptor
     */
    URL getURL() throws IOException;

    /**
     * @return a URI handle for this resource.
     * @throws IOException if the resource cannot be resolved as URI,
     *                     i.e. if the resource is not available as descriptor
     */
    URI getURI() throws IOException;

    /**
     * @return a File handle for this resource.
     * @throws IOException if the resource cannot be resolved as absolute
     *                     file path, i.e. if the resource is not available in a file system
     */
    File getFile() throws IOException;

    /**
     * @return the content length for this resource.
     * @throws IOException if the resource cannot be resolved
     *                     (in the file system or as some other known physical resource type)
     */
    long contentLength() throws IOException;

    /**
     * @return the last-modified timestamp for this resource.
     * @throws IOException if the resource cannot be resolved
     *                     (in the file system or as some other known physical resource type)
     */
    long lastModified() throws IOException;

    /**
     * @param relativePath the relative path (relative to this resource)
     * @return the resource handle for the relative resource
     * @throws IOException if the relative resource cannot be determined
     */
    Resource createRelative(String relativePath) throws IOException;

    /**
     * Determine a filename for this resource, i.e. typically the last
     * part of the path: for example, "myfile.txt".
     * 
Returns {@code null} if this type of resource does not
     * have a filename.
     *
     * @return the file name.
     */
    String getFilename();

    /**
     * @return a description for this resource,
     * to be used for error output when working with the resource.
     * Implementations are also encouraged to return this value
     * from their {@code toString} method.
     * @see Object#toString()
     */
    String getDescription();

}